The remarkable enchainment cooperativity effects displayed by single-site group 4 bimetallic olefin polymerization catalysts include significantly enhanced activity, chain branching, and comonomer enchainment selectivity. Moreover, these effects scale approximately inversely with the intermetallic distance, and are evident in both constrained geometry and aryloxyiminato group 4 catalysts, as depicted below for Ti2 and FI2—Zr2, respectively.

However studies to date have focused exclusively on group 4 metals. There remains an on-going effort in the art to extend such catalysts to include other metal centers to better realize the benefits and advantages available from such systems.